Hyperthyroidism in Cats: Symptoms & Recommended Diet

The thyroid is an important part of your cat's body that helps to regulate the various hormones. Hyperthyroidism occurs when the hormone levels are elevated above normal and cause a variety of concerns. Today our Montecito vets discuss the symptoms of hyperthyroidism in cats and how a modified diet may help.

Hyperthyroidism in Cats

The thyroid glands are located in your cat's neck which produce a variety of hormones that help to regulate many processes in the body, and control your cat's metabolic rate. If the thyroid produces too much or too little of these hormones your cat will either show symptoms of hypothyroidism (low levels of hormone) or hyperthyroidism (too much hormone).

Hyperthyroidism in cats causes their metabolism to speed up. This means that your cat will tend to burn energy too quickly, no matter how your cat seems to be eating they may be consistently losing weight.

Symptoms of Hyperthyroidism in Cats

While male and female cats are equally affected by hyperthyroidism, it most commonly affects cats that are older, typically over the age of 12.

The symptoms of hyperthyroidism in cats are usually subtle to start and gradually become more severe over time. Other underlying health issues can also complicate or mask symptoms of hyperthyroidism, so it’s important to see your vet early if your cat shows any of the symptoms listed below. Cats producing too much thyroid hormone may show one or more of the following symptoms:

When the condition becomes more advanced, some cats will pant when they are stressed which is unusual for cats. Although most cats suffering from hyperthyroidism have a good appetite and are restless, others may feel weak, lethargic or experience a lack of appetite. 

Causes of Hyperthyroidism in Cats

For most cats, hyperthyroidism is caused by a non-cancerous tumor located somewhere on the thyroid gland. In some rare cases, however, the tumor can develop into thyroid cancer.

Are there any lifelong complications resulting from hyperthyroidism?

Left untreated, hyperthyroidism affects the function of the heart and could possibly cause heart failure.

Your cat may also develop high blood pressure as a result of hyperthyroidism. Though we see this less often, high blood pressure in cats is linked to other serious health concerns such as damage to the brain, kidneys, heart and eyes. If your kitty is diagnosed with hypertension in addition to hyperthyroidism, medication will be required to their control blood pressure.

Hyperthyroidism and kidney disease often occur at the same time in older cats. When both these conditions are present, they need to be closely monitored and managed as managing hyperthyroidism can sometimes adversely affect kidney function.

Diagnosing Hyperthyroidism in Cats

Diagnosing hyperthyroidism in older cats can be somewhat tricky. Your vet will complete a physical exam and palpate your cat’s neck area to look for signs of an enlarged thyroid gland. At Montecito Pet Hospital our veterinary internal medicine team uses state-of-the-art diagnostic testing to help diagnose your pet's condition and provide advanced care.

Because there are a range of conditions that share the clinical symptoms of hyperthyroidism, a variety of tests may be used to diagnose your cat's condition. A complete blood count (CBC) urinalysis and chemistry panel can help rule out kidney failure and diabetes. A simple blood test showing elevated T4 levels in the bloodstream may be enough for a definitive diagnosis. Your vet may also check your kitty’s blood pressure or perform an electrocardiogram, chest x-ray or ultrasound.

Treatment for Hyperthyroidism in Cats

Depending on the results of your cat's tests, your vet may choose one of several treatment options for your cat’s hyperthyroidism.  They may include:

• Radioactive iodine therapy (likely the safest and most effective treatment option)
• Antithyroid medication
• Surgery to remove the thyroid
• Modified diet

Is a modified diet able to help manage hyperthyroidism in cats?

Hyperthyroidism in cats can often be managed through an iodine-restricted prescription diet from your vet. Iodine intake is necessary for the production of thyroid hormones, so the goal of an iodine-restricted therapeutic diet is to help reduce the production of thyroid hormones by reducing iodine in your cat's diet.

Strict adherence to the low-iodine diet is necessary for this treatment to be effective, which can prove challenging for some pet parents and their cats. Along with feeding your cat prescription food, you will need to strictly monitor your cat's treats, and prevent your cat from hunting for their own meal while outside.

Some studies show that after three weeks of following a prescription hyperthyroidism diet, levels of thyroid hormones begin to decrease, and within a few months, they may even return to normal levels.

Prognosis for Hyperthyroidism in Cats

If the condition is diagnosed and treated early, the prognosis for cats suffering from hyperthyroidism are generally good. In some cases where the condition has become more advanced, complications with other organs can worsen the prognosis.

Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.